fix: handle non-object entries in keyed reconcile

[cyphercodes]

Summary

• Fix keyed reconcile in @solidjs/signals so array entries that are null, undefined, or primitives are treated as direct values instead of being wrapped as store objects.
• Preserve keyed object reconciliation for wrappable entries while replacing non-object entries safely.
• Add regression coverage for nullable keyed arrays and object-to-primitive array replacement.

Closes #2772

How did you test this change?

• pnpm --dir packages/solid-signals exec vitest run tests/store/reconcile.test.ts
• pnpm --filter @solidjs/signals test
• pnpm --filter @solidjs/signals build
• pnpm exec prettier --check packages/solid-signals/src/store/reconcile.ts packages/solid-signals/tests/store/reconcile.test.ts
• git diff --check
• pnpm test

[changeset-bot]

⚠️ No Changeset found

Latest commit: a50b451

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR